The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Hot-fill plastic containers, such as those manufactured from polyethylene terephthalate (“PET”), have been commonplace for the packaging of liquid products, such as fruit juices and sports drinks, which must be filled into a container while the liquid is hot to provide for adequate and proper sterilization. Because these plastic containers are normally filled with a hot liquid, the product that occupies the container is commonly referred to as a “hot-fill product” or “hot-fill liquid” and the container is commonly referred to as a “hot-fill container.” During filling of the container, the product is typically dispensed into the container at a temperature of at least 180° F. Immediately after filling, the container is sealed or capped, such as with a threaded cap, and as the product cools to room temperature, such as 72° F., a negative internal pressure or vacuum pressure builds within the sealed container. Although PET containers that are hot-filled have been in use for quite some time, such containers are not without their share of limitations.
One limitation of PET hot-fill containers is that because such containers receive a hot-filled product and are immediately capped, the container walls contract as a vacuum pressure increases during hot-fill product cooling. Because of this product contraction, hot-fill containers may be equipped with vertical columns and circumferential grooves. The vertical columns and circumferential grooves, which are normally parallel to the container's bottom resting surface, provide strength to the container to withstand container distortion and aid the container in maintaining much of its as-molded shape, despite the internal vacuum pressure. Additionally, hot-fill containers may be equipped with vacuum panels to control the inward contraction of the container walls. The vacuum panels are typically located in specific wall areas immediately beside the vertical columns, and immediately beside and between the circumferential grooves so that the grooves and columns may provide support to the moving, collapsing vacuum panels yet maintain much of the overall shape of the container. Because of the necessity of the traditional vacuum panels in the container wall and support grooves above and below the vacuum panels to assist in maintaining the overall container shape, incorporating contour hand grips and other contours in the container wall, while preserving the ability of the container wall to absorb internal vacuum, is limited.
What is needed then is a hot-fill container with a wall that is capable of moving to absorb internal vacuum pressure in response to cooling of an internal hot-fill liquid and capable of maintaining the overall shape of the container while providing a contoured hand grip area.